1、一、can / could1. 表示请求和允许（permission） ，could 语气更委婉。Can / Could I use your dictionary?Yes, I can. (回答时通常用 can, 不用 could)“You _ borrow my notes provided you take care of them,” I told my friend.A. could B. should C. must D. can (口语多用)2. 表示能力（ability）She can swim, but she couldnt last year. (can 表现在或将来，c
2、ould 表过去)3. can 和 be able to 的异同 表示“能力” ，两者可互换 语法上，can 属于情态助动词（ modal auxiliary verb） ，它只有现在和过去两种时态形式，而 be able to 属于半助动词（semi- auxiliary verb） ，它有较多的时态形式，而且还可与其它情态助动词连用。You might be able to persuade her. 你也许能说服她。 在针对过去情况时，两者的区别意义明显，不可混用。could do 表示过去的一般能力，而 was/were able to 表示做某件具体事情的能力，相当于 managed
3、 to 或 succeeded in.We could save his life. 我们有办法救活他。 （但未必实施）We were able to save his life. 我们得以救活他。 （付诸实施）The fire spread through the hotel very quickly but everyone was able to (could) get out. 火势蔓延速度非常快，但是每个人都得以逃出酒店。4. 表示可能性（possibility），常用于否定句、疑问句或惊叹句中。He cant know my dress because Ive moved it t
4、o another place. (不可能)What can he be doing all this time? 他会是一直在干什么呢？If youre not careful, you could get into even worse trouble. (可能会陷入更大的麻烦)-The door was open.-It _ open. I had locked it myself and the key was in my pocket.A. cant be B. mustnt C. cant have been D. mustnt have been（“must + have + 过
5、去分词”表示对过去发生的事情或状态进行推测,语气比较坚定，通常只用于肯定句; “can / could + have + 过去分词”表示对过去某种情况的推测，一般用于否定句和疑问句。 ）He _ the 8:20 bus because he didnt leave home till 8:25.A. couldnt have caught (否定推测) B. ought to have caught (本应该)C. shouldnt have caught (本不该) D. must not have caught二、may / might1. 表示允许（permission）- May I
6、 ask you where you were born?- Yes, you may. / No, you mustnt / may not. 可以。/ 不可以。2. 表示可能性（possibility） ，常用于肯定句（疑问句和否定句常用 can）.It may / might be true. (现在)He may / might get there in time, but Im not sure. (将来)Linda may / might have missed the train. (过去)I dont know whether he is there. He may / mig
7、ht not be there.He _ unwisely, but he was at least trying to do something helpful.A. may have acted (肯定程度弱 ) B. must have actedC. should act D. would act3. may 可用来表示祝愿 May you succeed! 4. may / might as well 不妨，还是 的好Since it is raining hard, you may as well stay here. Since the weather is fine we _
8、walk for a while.A. may B. mustC. might as well D. will三、will / would1. 表示建议 （suggestion） ，用于第二人称疑问句中。would, wont 的语气更委婉，不表时态。- Will / Would you lend me your pen?- Certainly I will. (表示接受请求只能用 will，不可用 would)Wont you come in?2. 表示意愿、意图、决心、承诺等。I will do my best. (promise)We will never do it again. (d
9、etermination)Which will you take? (willingness)I told Peter that I would go along with him. (willingness)3. will 表示习惯性动作或某种倾向，过去时用 would，相当于 used to.Tom will talk for hours if you give him the chance. She would (= used to) listen to music when she was in low spirits.四、shall1. shall 用于第一、第三人称疑问句中,表示说
10、话人征求对方的意见或向对方请示。The room is so dirty. Shall we clean it?Shall he come tomorrow? 明天需要他来吗？2. Shall 用于第二、第三人称,表示说话人给对方命令、警告、允诺或威胁。You shall do it, whether you want to or not. (order)Tell him that he shall have the book as soon as I finish it. (promise)You shall pay for it. (threat)五、should1. 表示劝告，建议时，意
11、为“应该” ，与 ought to 通用；但表示道义上的责任、义务时只能用 ought to。We should / ought to learn about the computer and make full use of it. You are his father. You ought to take care of him. 2. 表示推测、可能时，往往有一定的根据，含有“按道理应该”之意。They should be at home by now for they have been away for 2 hours. 3. should 有时表示说话人的感情、情绪。Why sho
12、uld I go? (dissatisfaction)I was shocked that she should have said such a thing to you. (surprise)I am sorry that she should be so stubborn. (disappointment)I am surprised _ this city is a dull place to live in.A. that you should think B. by what you are thinkingC. that you would think D. with what
13、you were thinking六、must1. 表示必须（necessity） ，语气比 should 强烈；对于 must 的提问，否定回答用neednt 或 dont / doesnt have to ; 否定的 mustnt 表示禁止，有时表示劝告或主张。- Must I hand in my work now?- Yes, you must. / No, you neednt / dont have to.You mustnt drive so fast. （禁止）You mustnt miss the movie. Its great.（建议）2表示推测（deduction） ，
14、must 只用于肯定句中，在否定句和疑问句中用 cant / couldnt 和 can / could.The light is on. She must be in the office.He must be doing his homework now.- She must be in the dormitory now.- No, she _ be there. I saw her in the classroom a minute ago.A. mustnt B. cant C. couldnt D. wouldnt七、needneed 用作情态动词，表示必要， neednt 表示不
15、必，通常用于疑问句和否定句中。对于 need 引起的疑问句，肯定回答用 must，否定回答用 neednt。Its only 8 oclock. Need you go so early?There neednt be any arguments about this question.-Need they fill the form?- Yes, they must. / No, they neednt.八、daredare 用作情态动词，后跟动词原形，主要用于疑问句、否定句和条件句中。My sister dare not go out in such a dark night.Dare y
16、ou catch the mouse?How dare you speak to me like that?If you dare do it, I would vote for you.九、情态动词+have+ 过去分词1. must have done，对过去有把握的推测，其否定形式为 cant / couldnt have done.I must have seen you somewhere, but I cant collect your name.The room is in a terrible mess; it cant have been cleaned.2. may / m
17、ight have done, 对过去不太有把握的推测He may have had some training in Chinese Kungfu.3. could have done 本可以，本能够I felt so regretful. I could have helped him.4. should have done / ought to have done 本该做I ought to have known he would do a silly thing like that.5. neednt have done 本不必做You neednt have woken me up; I dont have to work today.You _ Mark anything. It was none of his business.A. neednt have told B. neednt tellC. mustnt have told D. mustnt tell
